Increasing emphasis is placed on the accuracy and precision in manufacturing and assembly processes, particularly in the field of passenger vehicles. Demand for higher volumes of vehicles and efficient manufacturing and assembly of such vehicles has also increased, further straining the objectives of accuracy, precision and quality of the end product.
In the assembly of passenger vehicles, the building block is the skeletal body, still often made of formed sheet steel components and subassemblies. Modern assembly plants require hundreds of sequential build stations positioned along a progressive assembly line. As the vehicle body is built, it is essential that the vehicle body be accurately and precisely positioned at each individual assembly station so the automation, robots or human operators can accurately and precisely position and mount the components or subassemblies at each station.
Transporting and positioning the vehicle body has been accomplished in many ways. A preferred way is by a moving pallet that has pillars or risers, typically four or six to a pallet, which the skeletal body is positioned and sits atop of as it moves from station to station on the pallet. In order to achieve a predictable and accurate placement of the vehicle body at any one sequential build station, the skeletal vehicle body must first be fixedly positioned to the pallet and then second, the pallet and secured vehicle body must be positioned in the predetermined three-dimensional location at a particular build station so that the assembly operations at that station can be carried out. To the extent that a vehicle body must be loaded onto and removed from the pallet at various points along an assembly line, for example, transfer to another pallet or device for further processing along another assembly line, it is advantageous for the vehicle body to be loaded and locked to the pallet, or unlocked or unsecured from the pallet and removed from the pallet.
Various systems and operations for securing a vehicle body to a pallet and locating a pallet at sequential build stations have been proposed. One example is the Single Geometry Palletized Framing System described and illustrated in U.S. Patent Application Publication No. 2009/0289043 assigned to Comau, Inc., assignee of the present invention, the entire contents of which are incorporated herein by reference. Additional systems and operations for remotely securing a vehicle body to pallet are described and illustrated in U.S. Patent Application Publication No. 2011/0138601 assigned to Comau, Inc., assignee of the present invention, the entire contents of which are incorporated herein by reference.
A disadvantage in prior systems has involved complex hydraulic, pneumatic and other mechanisms secured aboard the moving pallet which fixedly secure and unsecure, as desired, the vehicle body to the pallet along the path of assembly. These systems require additional components to be added to the pallet and moved along with the pallet throughout the assembly process.
Another disadvantage is the possibility that the system used to secure the body to the risers, for example a hook, has not engaged the body as designed. For example, it is possible that due to misalignment between the body and the pallet, build variances, or malfunction of the system, that one or more of the hooks has not engaged the body or has not done so as designed. Prior systems would require a visual inspection which requires additional personnel or expensive vision equipment to view a difficult area to inspect underneath the vehicle body as the pallets continuously move down an assembly line. Although some conventional systems indicate a position of an actuation mechanism for the hook, they do not provide a positive indication of whether or not the hook is actually engaged with the body.
It would be advantageous to improve upon prior systems which secure a vehicle body to a pallet or structure that is moved along an assembly line and to accurately position the pallet and secured body at vehicle build stations. It would be advantageous to have a remote system for selective securing or locking the vehicle body to the pallet which does not require pneumatic or hydraulic mechanisms to actuate components on the pallet to secure the body. It would be further advantageous to have a system to secure the vehicle to the body that provides a positive indication that each of the hooks is either open (in a non-engaged position to allow installation or removal of the body on the risers) or closed (in an engaged position with the body). It would further be advantageous to design alternate methods for locating and securing the pallet at vehicle stations to better accommodate particular vehicle builds and body styles.